i40iw: Do not access pointer after free

Child_listen_node pointer is used in a debug print after kfree.
Move the print before kfree.

Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>